1. Field of the Invention
The present invention relates generally to hinges and similar attachments. More specifically, the present hinge is configured particularly for use with a “drop down” oven door (although it is adaptable to other structures), and acts to release the door suddenly and rapidly from its fully open horizontal position in the event that an excessive load is placed upon the door. This function prevents tipping of the oven due to the door acting as a lever, and/or the use of the door as a step by a child to access the top of the stove.
2. Description of the Related Art
Most household ovens are constructed with a “drop down” oven door, i.e., the door is hinged along its lower edge or at the ends thereof. This allows articles, such as large pans, oven racks, etc., to be placed on the inner surface of the oven door when the door is fully lowered to its horizontal position as the article is moved into or from the oven proper, as in normal use of the oven. However, ovens and oven doors are also subject to abnormal use, i.e., an excessively high load being placed on the oven door. This may occur in the event of one or more toddlers or small children using the oven door as a step to reach for something on the range top of the stove. While this is by no means a proper use of the oven and door, it nevertheless may happen from time to time. A number of tragedies in which one or more small children have spilled hot liquids, oils, etc., on themselves from the range top of a stove have been documented in the past. Free-standing range/oven appliances are designed to be firmly anchored to the adjacent building structure, but anchors are often not installed, perhaps in the majority of oven installations. As a result, even if the door structure remains intact structurally, with no deformation or breakage, the entire oven may tip, causing articles atop the stove to slide forward.
As a result, ANSI (American National Standards Institute) and UL (Underwriters Laboratories) have developed standards for oven doors for both normal and abnormal use. The ANSI standard is Z21.1, directed to gas ranges, while UL standard 858 covers electric ovens and ranges. The normal test requires that the oven door support, without the oven tipping, a 75-pound load applied mid-span of an open oven door with a maximum of one-half inch deflection of the door at six inches from the hinge line of the door. This normal requirement assures that the door will support a normal load thereon, e.g., a large turkey or roast, etc., without the door or hinge structure bending and deflecting sufficiently to allow the load to slide off and drop to the floor. The loading for this test is well below that required by safety standards to prevent tipping of the oven or damage to the door structure, and in fact the normal use test requires that the door survive the test without breakage or damage.
The abnormal use test is intended to assure that the oven will remain upright when a load of up to 250 pounds is placed on the door, as when one or more toddlers or small children may open the door and use it as a step to access the top of the stove. In the abnormal use test, deformation, deflection, and breakage of the door, door hinge structure, attachment structure, etc., is permissible, so long as the door has passed the 75-pound load test for normal use. The primary concern here is that an article placed upon the cook top of the stove should not slide off the top of the stove due to tilting of the stove or oven during this test. The oven is, of course, firmly anchored to the underlying structure during the abnormal use test, with this test serving to check the anchoring system and overall rigidity of the oven structure.
However, it is recognized that a large number of ovens, likely the majority, are not properly anchored to the floor during installation, even where such anchoring is required by building codes. As a result, it is possible for an oven that passes the abnormal use test with the door and hinge structure intact to tip if a large load is placed upon the door. The tragedy that may result from this if small children climb upon the door and spill hot oil or other liquids upon themselves, or if the entire oven tips forward toward them to allow hot liquids to be dumped onto them from the range top surface, has been noted further above.
A number of different oven door hinge configurations have been developed in the past as a response to the above problem. In some cases, a supplemental spring(s) is used to allow the door to open past the horizontal when an excessive load is placed upon the door. However, due to the spring constant, the door will lower only slightly beyond the horizontal when a weight only slightly exceeding the predetermined maximum for the horizontal door, is placed thereon. Thus, no substantial deflection of the door from the horizontal is provided with such a configuration until a weight substantially greater than the predetermined maximum for the horizontal door is placed thereon. It is difficult to design a door using such a supplemental spring configuration which will remain undeflected from the horizontal while supporting a load of 75 pounds, and yet will allow the door to drop down significantly when a load only slightly greater, i.e., a toddler or small child, places his or her weight upon the door. Some oven doors are designed with a spherical fitting that pulls through a slot extending from a socket in order to widen the slot and spread the jaws when excessive load is placed upon the assembly. In this structure, the deformation of the slot permits a slow deflection of the door assembly well before the point is reached where the fitting separates from its attachment point.
There is a need for a hinge configuration for a “drop down” oven door having a hinge axis along its lower edge, in which the hinge configuration precludes any breakage or substantial deformation of the door and hinge structure in testing according to ANSI and UL standards of normal use. Moreover, the hinge configuration should provide a sudden failure mode, allowing the door to drop completely until its distal edge contacts the underlying surface, or the door is stopped in some other manner, when a single, simple, easily replaced part (which may be considered to be a “mechanical fuse”) fails at a predetermined load in abnormal use testing. The sudden failure mode must remain completely intact with no significant deflection until sufficient force is applied to cause the sudden and complete failure of the “mechanical fuse.”
Thus, a load limiting hinge solving the aforementioned problems is desired.